This invention relates to liquid level transducers, and more particularly to a liquid level transducer having a float that moves in response to a change in liquid level and a method of constructing the liquid level transducer.
Transducers for measuring liquid level are often used in vehicles, industrial equipment, as well as other mobile and stationary systems and components. The electrical output of such transducers varies in response to a change in the liquid level being measured and is typically in the form of a change in resistance, capacitance, current flow, magnetic field, and frequency. These types of transducers may include variable capacitors or resistors, optical components, Hall Effect sensors, strain gauges, ultrasonic devices, reed switch arrays, and so on.
For reed switch-type devices, a plurality of reed switches are usually arranged in series with a plurality of resistors along the length of a circuit board. The reed switches are normally responsive to the presence and absence of a magnetic field for opening and/or closing the switch. A float rides along the surface of the liquid to be measured and is constrained to move in a linear direction along the circuit board. The float usually includes an embedded magnet to trip one of the reed switches as the float moves in response to a change in liquid level in the tank. Thus, the resistance of the circuit, which is indicative of liquid level, depends on the position of the float and the particular reed switch that has been tripped.
However, such devices typically have several drawbacks. For example, it is known that reed switches suffer from hysteresis effects and may open and/or close prematurely depending on the orientation of the reed switches with respect to the magnet, the magnetic strength of the magnet, the distance between the reed switch and the magnet, and so on. When the reed switches are aligned linearly, each reed switch may open and close up to three times as the float approaches, aligns with, and passes each reed switch, thus leading to improper liquid level indication, undesired switching, and premature failure of the switches. In addition, prior art solutions expose the reed switches to the liquid being measured, which may be corrosive and cause inaccurate liquid level readings and premature failure. It would therefore be desirable to overcome at least some of the disadvantages associated with prior art reed switch-type liquid level transducers.
In addition, prior art liquid level transducers that include a mounting head and an elongate sensor probe, such as a reed switch probe, resistor probe, capacitor probe, and so on, are often difficult and time-consuming to assemble due to the number of individual components and the fastening means associated with each component. It would therefore be desirable to provide a liquid level transducer that is easier to assemble and has relatively fewer parts.